Cutting simulation with consideration of the material hardening in the Shear Zone of AISI1045

By the use of high energy synchrotron X-ray diffraction it was possible to determine the stress state in the chip formation zone during orthogonal cutting of AISI1045. The analysis of the diffractograms showed a hardening of the material during the movement through the shear zone. For this reason nano indentation experiments on prepared chips have been carried out. With these experiments, the material hardening has been confirmed. The nano indentation experiments were reproduced by FEM simulations and it was possible to determine flow curves of the hardened material above the shear zone based on existing flow curves of AISI1045. Thus, cutting simulations have been carried out, which considered the material hardening in the shear zone. The simulation results were then compared with the results of the in-situ strain measurements

Cutting Simulation with Consideration of the Material Hardening in the Shear Zone of AISI1045

By the use of high energy synchrotron X-ray diffraction it was possible to determine the stress state in the chip formation zone during orthogonal cutting of AISI1045. The analysis of the diffractograms showed a hardening of the material during the movement through the shear zone. For this reason nano indentation experiments on prepared chips have been carried out. With these experiments, the material hardening has been confirmed. The nano indentation experiments were reproduced by FEM simulations and it was possible to determine flow curves of the hardened material above the shear zone based on existing flow curves of AISI1045. Thus, cutting simulations have been carried out, which considered the material hardening in the shear zone. The simulation results were then compared with the results of the in-situ strain measurements

Forming mechanisms-related residual stress development in single point incremental forming

The mechanical properties of a component are significantly influenced by the prevailing residual stress state. A deliberate induction of compressive residual stresses or a reduction of tensile residual stresses can improve the component properties, such as fatigue strength. Single point incremental forming is a flexible manufacturing process to produce complex shaped parts by the computerized numerically controlled movement of a hemispherical forming tool. Because the process parameters can be locally adjusted it is possible to influence the residual stress state of the component. The influence of the forming mechanisms bending, shearing and membrane stretching, as well as the role of the hydrostatic compression on the residual stress state is widely unknown. This work aims to fill this gap. Therefore, linear grooves are formed into AA5083 sheets in a single-stage incremental forming process. The residual stress state of the unclamped sheet is measured on both sides of the groove center by means of X-ray diffraction. The relative intensity of the dominant forming mechanism is adjusted by adapting the relevant process parameters step-down increment Δz and tool radius R$_{Tool}$. The forming mechanisms are analyzed numerically by splitting the total plastic energy into the three forming mechanisms bending, shearing and membrane stretching. The numerical results for bending and membrane stretching could be validated by crystallographic analysis. A shift in the energy ratio of the forming mechanism from bending to shearing with increasing relative step-down increment $Δz/R_{Tool}$ could be observed numerically. The maximum residual stress amplitudes are found for $Δz/R_{Tool}$ < 1. The results indicate that a deliberate residual stress state can be induced by adjusting the dominant forming mechanism of the process

An extended shear angle model derived from in situ strain measurements during orthogonal cutting

There are numerous cutting models which describe the chip formation process. However, they are based on a number of simplifying assumptions. In order to verify these assumptions and to get a better understanding of the cutting process, the different stress states in the chip formation zone were determined by means of diffraction experiments with monochromatic high-energy synchrotron X-radiation during orthogonal, quasistatic cutting of the material C45E. The results from the experiments are compared with simulated stresses. The experimental data indicate that the assumption of a free chip flow according to the shear angle model of Opitz and Hucks is not valid. The model was therefore extended considering the normal stresses in direction of the chip flow